As a runflat tire capable of traveling for a relatively long distance in a deflated condition that the tire loses air pressure due to a puncture, there is known, for example, a tire of so-called side-reinforced type wherein a side-reinforcing rubber layer having a crescent-shaped cross section is disposed in each sidewall portion (see for example Patent Literature 1). In the runflat tire of this type, a plurality of carcass plies are used in order to enhance a load-supporting ability. Further, a rayon fiber cord which has a good heat resistance is used as a carcass cord in order to secure a durability in runflat mode, since the tire temperature in runflat mode is very high as compared with that during normal running in the inflated state.    Patent Literature 1: JP 2000-351307 A